1. Field of the Invention
The present invention relates generally to tubular endoluminal prostheses, such as grafts, stents, stent-grafts, and the like. More particularly, the present invention provides methods, systems, and devices for sealing or occluding a branch of a branching endoluminal prosthesis, particularly when the branch to be sealed has been found to be incorrectly positioned, inaccessible, or otherwise detrimental to a prosthetic therapy for abdominal and other aneurysms, and for treatments of other branched body lumens.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition, which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending into one or both of the iliac arteries.
Aortic aneurysms are most commonly treated in open surgical procedures, where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of the usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and requires experienced surgeons and well equipped surgical facilities. Even with the best surgeons and equipment, however, patients suffering from such aneurysms are often elderly and weakened from cardiovascular and other diseases, which reduces the number of eligible patients. Even for eligible patients prior to rupture, conventional aneurysm repair has a relatively high mortality rate, usually from 2 to 10%. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery takes several weeks and often requires a lengthy hospital stay.
In order to overcome all or some of these drawbacks, a variety of endovascular prosthesis placement techniques have been proposed for the treatment of aneurysms. Although some of these proposed techniques appear very promising, known methods and apparatus suffers from undesirable limitations in at least some aspect. Of particular relevance for the present invention, endovascular therapies for aneurysms which extend from the abdominal artery down along one or both iliac arteries, sometimes called aortoiliac aneurysms, have proven to be particularly problematic.
Endovascular therapies for aortoiliac aneurysms are complicated by the difficulty of sealing the aneurysm from the blood flow through the aorta and the first and second iliac arteries, while maintaining that blood flow to the separate branches of the vascular system. One approach which has been used to isolate such aneurysms was described by Dr. Parodi in "Endovascular Repair of Abdominal Aortic Aneurysms and Other Arterial Lesions", J. Vasc. Surq. 21:549-57 (April, 1995). This "single-lumen" method involved deploying an unbranching tubular prosthesis from the healthy aorta above the aneurysm, through the aneurysm itself, and into one of the two iliac arteries, so that all blood flowing through the aorta was channelled into that single iliac. A portion of the blood is then transferred to the alternate portion of the vascular system (normally supplied by the alternate iliac) through a "femorofemoral bypass," a prosthetic vascular graft having an end-to-side anastomosis with each of the femoral arteries. Advantageously, known femorofemoral bypass procedures involve substantially less patient trauma than conventional invasive aortic aneurysm repair. The unused iliac artery is then occluded with detachable balloons or ligation.
Although this single-lumen method has proven to be fairly effective, the resulting blood flow path is somewhat less than ideal. The entire aortic blood flow must pass through a single iliac artery, and then separates downstream of the hypogastric artery into left and right femoral portions, providing a tortuous route which imposes a significant strain on the heart. Nonetheless, this procedure does have the advantages of only requiring a single healthy iliac artery for the endoluminal prosthesis to seal and anchor against, and is clearly preferable to allowing blood to continue to flow into a weak or ruptured aneurysm.
More recently, endovascular deployment of a bifurcated tubular prosthesis has been proposed as a therapy for aortoiliac aneurysms. Bifurcated prostheses generally have a trunk portion with a relatively large lumen for deployment in the aorta, and first and second branch portions with smaller branch lumens for deployment within each of the iliac arteries. The deployed trunk and branch portions preferably seal to each other and to the healthy vascular walls beyond the aneurysm to isolate the aneurysm from the bloodstream. Advantageously, the aortic blood flow enters the trunk prosthetic lumen, is separated into the two branch prosthetic lumens, and then flows into each of the iliac arteries in a path that approximates that of a normal, healthy vascular system. Unfortunately, deployment of such bifurcated prostheses across the aortoiliac junction is more complex than deployment of a single-lumen prosthesis.
A variety of minimally invasive techniques have been suggested for deployment of these bifurcated prostheses, including in situ assembly of multiple prosthetic modules, initial positioning of both prosthetic branch portions within a single iliac artery, initially deploying one of the branches folded up along the aorta, or the like. Regardless of the specific deployment procedure used, a tubular prosthesis having a lumen initially spans from the healthy portion of the aorta, through the aneurysm, and into one of the two iliac arteries, as was also true of the single-lumen prosthetic method. However, these techniques differ from the single-lumen method in that a branch port for the alternate iliac artery is disposed between the upstream and downstream ends of the tubular bifurcated prosthesis. Furthermore, proper initial deployment of the bifurcated prosthesis generally requires that the second branch port be properly oriented toward the alternate iliac.
Completing deployment of the bifurcated prosthesis generally involves positioning of the second branch portion in the alternate iliac. Oftentimes, the second branch portion is deployed through a catheter which extends from the iliac to the branch port of the bifurcated prostheses, thereby assembling the continuous bifurcated prosthetic lumen in situ. Such deployment of the second branch portion can be very straightforward, and in situ assembly of bifurcated prostheses appears to hold significant promise for many abdominal aortic aneurysm patients.
Unfortunately, bifurcated prosthetic therapies are not without their own disadvantages. Aortic aneurysms vary widely in location, size, and the distended shape of the aneurysm itself. Particularly in the advanced stages, aneurysms can also distort the aorta and iliac arteries surrounding the aneurysm, and tend to collect large amounts of thrombus. Diseased iliac arteries may be narrow due to plaque buildup, so that the remaining lumen is highly tortuous. In fact, diseased vessel tortuosity may prevent catheter or even guidewire passage. Furthermore, the precise shape and extent of the aneurysm can be very difficult to accurately determine. As a result, the accurate initial deployment of the bifurcated prosthesis, and in particular, the accurate orientation of the branch port, can be problematic. Even when the branch port is positioned as intended, it may turn out to be difficult and/or impossible to effectively deploy the second branch without rupturing the aneurysm, or without releasing the microthrombus from the distended aneurysm into the blood stream.
Once the physician completes initial deployment of a bifurcated prosthesis, but then finds that it is impossible to complete the deployment so as to seal off the aneurysm, massive surgical intervention is generally required to remove the partially deployed bifurcated prosthesis, and to install a conventional artificial graft. Hence, current minimally invasive bifurcated prosthetic therapies may be performed only after all the preparation, personnel, and equipment for convention aneurysm repair are in place. Clearly, such fallback requirements compromise the advantages of present bifurcated prosthetic therapies.
For these reasons, it would be desirable to provide improved endoluminal prosthetic methods, systems, and devices. It would be particularly desirable to provide endovascular therapies which would allow surgeons to take full advantage of the bifurcated prosthetic methods whenever possible, and to fall back to the single-lumen prosthetic methods when required by a particular patients physiology, or by the events as they actually unfold during initial deployment. It would further be desirable to provide methods and systems which would allow physicians to aggressively pursue the advantageous bifurcated prosthetic techniques, even when it is not entirely certain that those techniques will succeed, but to provide a less invasive fallback procedure if the complete deployment of the bifurcated prosthesis turns out to be impracticable.
2. Description of the Background Art
Co-pending U.S. patent application Ser. No. 08/615,697, filed Mar. 13, 1996, (Attorney Docket No. 16380-004100) the full disclosure of which is incorporated herein by reference, describes exemplary modular bifurcated prosthetic structures which are highly adaptable to a wide variety of patient physiologies. Provisional U.S. Patent Application Ser. No. 60/008,254, filed Dec. 1, 1995 (Attorney Docket No. 16380-003400), also incorporated herein by reference, describes bifurcated modular prosthetic structures and methods for assembling them in situ.
Dr. Parodi's article "Endovascular Repair of Abdominal Aortic Aneurysms and Other Arterial Lesions", J. Vasc. Surg. 21:549-57 (1995), has been described above. U.S. Pat. No. 5,499,995 describes a device and method for blocking a body passageway by inserting an expandable frame into the passageway and expanding the frame therein. U.S. Pat. No. 5,489,295, describes an endovascular graft having a bifurcation, and a method for deploying the bifurcated graft by pulling one leg from the aorta down into an iliac.